Emergency firearm firing mechanism for high velocity grenade rounds

ABSTRACT

FOR FIREARMS HAVING A HINGED BARREL, A FIRING MECHANISM INCLUDING A PRESSURE PLATE ACTUATABLE BY THE CARTRIDGE CASE SET BACK FOR AUTOMATICALLY COCKING THE FIRING PIN BY CARTRIDGE DISCHARGE AND A BARREL LATCHING DEVICE ENGAGEABLE WITH THE FIRING PIN FOR RETRACTION THEREOF TO ASSURE COCKING WHEN THE BARREL IS UNLATCHED FOR LOADING.

- Filed Dec. 6, 1968 March 2,. 1.971 s, D. sILsBY 3,556527 EMERGENCY FIREARM VFIRING MECHANISM FOR HIGH VELOCITY GRENDE ROUNDS v 3 Sheets-Sheet 1 March 2, 1971 s. D. slLsBY EMERGENCY FIREARM FIRING MECHANISM FOR HIGH VELOCITY GRENADE ROUNDS 3 Sheets-Sheet LS Filed Dec. 6, 1968 m T N E V m Sammy IJ- aflshy BY MTV- 7 /VI- S I X W ATTORNEY United States Patent O U.S. Cl. 42-41 7 ClamS ABSTRACT OF THE DISCLOSURE For firearms having a hinged barrel, a firing mechanism including a pressure plate actuatable by the cartridge case set back for automatically cockng the firing pin by cartridge discharge and a barrel latching device engageable with the firing pin for retraction thereof to assure cockng when the barrel is unlatched for loading.

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

Most helicopters with offensive capabilities are armed with launchers for automatically firing 40 mm. grenade rounds such as the M3T84. These rounds have high Velocity Characteristics with long-range capabilities and consequently produce high recoil forces. They also require considerable amount of energy to ignite the primer. Consequently, because of these problems, it has not been possible to utilize these grenade rounds in conventional hand held firearms and therefore, although helicopters when shot down may have on board a large supply of these grenade rounds, they cannot be used by the crash survivors for defensive or offensive purposes when away from the launchers in the downed aircraft.

IT he problem of the excessive velocity and recoil forces has been successfully resolved by the invention which is the subject of my co-pending application for Emergency Weapon for Firing High Velocity Grenade Rounds, Ser. No. 873,426, filed Nov. 3, 1969. It is a principal object of this invention to provide a firing mechanism which is especially well adapted for use in such an emergency firearm.

It is another object of th-is invention to provide for a firearm, wherein the barrel is pivoted to an open position for loading a round thereinto .and which is locked in the closed firing position by a longitudinally sliding barrel latch, a firing mechanism having a firing pin which is cocked for initially charging the firearm by the barrel latch when the barrel is unlocked for loading a round thereinto and is therea-fter automatically recocked by set -back as hereinafter defined, of the case of the discharged round. Thus, the very considerable force required to cock the firing pin because of the energy required thereof to discharge the round is eliminated, thereby facilitating and hastening the reloading of the firearm. The term set back as herein applied is defined as the relative rearward displacement of a cartridge case in its chamber responsive to cartridge discharge.

Further objects and advantages of the invention Will be apparent from the specification and accompanying drawings which are for the purpose of illustration only and in which:

FIG. 1 is a fragmentary, partially cross-sectioned view of the emergency firearm showing the firing pin cocked and the trigger held by the safety against accidental discharge;

FIG. 2 is a view of the firing mechanism similar to that shown in FIG. 1 but showing the trigger pantially pulled to release the firing pin;

3,566,527 Patented Mar. 2, 1971 ice FIG. 3 is .a vie'w similar to F-IG. 2 but showing the firing pin released to strike the chambered round and the sear released from the trigger;

FIG. 4 is a fragmentary view similar to FIG. 3 but shows the pressure plate driven rearward by set back of the discharge energized round case and the firing pin held cocked by the sear with the finger piece still re'- tracted;

FIG. 5 is a view taken along line 5-5 of FIG. 3, and

FIG. 6 is an exploded view of the firing mechanism.

Shown in the drawings is a firearm 12 comprising a stock 14, a tubular receiver 16 extending forward therefrom and a barrel 18. Receiver 16 is provided With a forwardly extending ledge 20 having hinge means 22 at the front end to mount barrel 18 along the length thereof for pivotal displacement between an open position, wheretin the breech end is swung outwardly for loading a grenade round 24 thereinto, and a closed firing position. Barrel 18 is rele'asably locked in the closed firing position by a latch 26 mounted in the upper part of receiver 16 .for longitudinal displacement between a forward locking position and a rearward unlocked position. When in the looking position latch 26 extends over barrel 18 to block pivotal displacement thereof from the firing position. Latch 26 is spring biased to the looking position and is manually actuated to the unlocked position by a lever 28 to be fully described hereinafter.

IRound 24 is fired by a firing mechanism 30 which is assembled within a breechblock 32 housed within receiver 16. The front end of breechblock 32, noted at 34, is spaced from the front end of receiver 16 to form a chamber 36 for receiving a pressure plate 38 so that it is displaceable therein between a forward and a recoil position. The forward displacement of pressure plate 38 Flange 40 is located so that the front face of pressure is limited by contact of a circumferential flange 40 therearound with an internal circular rib 42 in receiver 16. plate 38, when in its forward position, has contact with the base of round 24 when barrel 18 is closed. Pressure plate 38 is biased to its forward position by three coil springs 44 and is driven to its rearward position by set back of case 46 of round 24 when fired.

Round 24 is fired by a firing pin 48 consisting of a cylindrical body 49 which is slidingly received by a mating longitudinal bore in breechblock 32, a striker portion 50 extending coaxially forward therefrom and an annular shoulder S2 formed at the front end of the body around the striker portion. Striker portion 50 is extendable through a mating orifice 53 in pressure plate 38 to strike round 24 for discharge thereof and so that shoulder 52 is contactable by the rear face of the pressure plate. A bore 54 extends forwardly into body 49 from the rear end thereof to a wall 56 and such |bore receives a compression spr-ing 58 which bottoms thereagainst. Spring 58 receives in turn a plunger-guide 60 that includes a head 62 which has contact with the rear end of the spring, a shaft 64 extending forwardly from the head into the spring to control the distortion of the coils thereof when extended, and a spherical knob 66. Knob 66 extends concentrically rearward from head 62 for engagement with sear 68 as hereinafter described. Spring 58 When compressed between Wall 56 and head 62 must store suflicient energy to transfer at least 5.5 in. l'bs. of energy to the primer of round 24 for ignition thereof when firing pin 48 strikes thereagainst.

Sear 68 is pivotally mounted in breechblock 32 on a transverse pin 70 which also pivotally mounts a cooperating trigger 72. Sear 68 is also displaceable longitudinally in a forward and a rearward direction on pin 70 by means of a longitudinal slot 74 in the sear through which such pin passes. Sear 68 and trigger 72 are both received by a slot 76 which extends upwardly into breechblock 32 from the underside thereof. Trigger 72 includes a dependng finger piece 77, a forward projection 78 and an upward extension 79. Sear 68 is of bell crank configuration with slot 74 located at the convergence of an upwardly extending first arm 80 and aforwardly extending second arm 82. A spherical pocket 83 in the front face of first arm 80 receives knob 66 to provide means for transferring the biasiof spring 58 to sear 68 for pivotal displacement thereby to its engaging position relative to firing pin 48. A hook on the end of second arm 82 is engageable with a notch 86 in body 49 of firing pin 48, when sear 68 is in its engaging position, to hold the firing pin retracted in its cocked position. A spring 88 is operationally disposed between first arm 80 of sear 68 and up- Ward extension 79 of trigger 72 for biasing forward projection 78 thereof upwardly and finger piece 77 forwardly.

[Forward projection 78 is terminated by a double-tang portion 90 with a pair of downwardly facing lips including a front lip 92 and a rear lip 94. Rear lip 94 is contactable with a catch 96 slidingly mounted in a longitudinal bore y98 in second arm 82 of sear 68 and is springbiased outwardly to an engaging position so that when finger piece 77 is pulled and forward projection 78 is consequently swung downwardly the contact of rear lip 94 with the catch rotates sear 68 to disengage hook 84 from notch 86 for release of firing pin 48. Cooperating cam surfaces 99 and 100, formed respectively on rear lip 94 and catch 96, cam catch 96 inwardly, permitting displacement of the rear lip thereby when finger Piece 77 is released to return to its normal forward position. Front lip 92 cooperates with a safety 101 disposed through breech lock 32 and receiver 16 for transversal displacement to releasably block accidental actuation of trigger 72.

-Firing pin 48 is manually retracted to its cocked position by lever 28 which also acts, as hereinbefore described, to unlock barrel 1-8. Lever 28 includes a rod 102 which is slidingly mounted in a mating bore 104 longitudinally located in breechblock 32. A bar 105 is fixed to the front end of rod 102 and is vertically disposed so that top end 106 thereof is received by a mating recess 107 in latch 26 and bottom end 108 is slidingly received by a longitudinal channel 110 in body 49 of firing pin 48. Channel 110 extends rearwardly from the front end of body 49 to a wall 112. Bore 104 is counterbored 'at 114 so as to receive the rear portion of a compression spring 116 Which has contact at its front end with bar 105 so as to bias lever 28 and latch 26 to the forward position. A handle 118 is fixed to rod 102 and extends upwardly from receiver 16 through opening 120 to provide means for manually pulling lever 28 rearwardly for unlocking barrel 18 -and intially cocking firing pin 48.

OPERATION When firearm 12 is to be intially fired, handle 118 is pulled rearwardly. This causes latch 26 to be displaced clear of barrel 18 which is thereby free to be swung to its open position for loading round 24 thereinto. At the same time, when handle 118 is pulled rearwardly, bottom end 108 of bar 105 contacts wall 112 of channel 110 in firing pin 48 so that rearward pull on the handle retracts the firing pin to its cocked position. When firing pin 48 reaches its cocked position, hook 84 on searl 68 is pressed into notch 86 through the bias of spring 58 thereagainst by means of plunger-guide 60. Firearm 12 is now ready to be fired when safety 101 is pressed inwardly to free trigger 72 for actuation.

Firearm 12 is fired by pulling on finger piece 77 which rotates trigger 72 to swing forward projection 78 thereof downwardly. The downward displacement of forward projection 78 presses rear lip 94 against catch 96, causing sear 68 to be rotated and thereby swing hook 84 clear of notch 86. This frees firing pin 48 which strikes forwardly under the influences of the compressed spring 58 to discharge round 24. Case 46 is set back responsive to the discharge forces against pressure plate 38 which is thereby displaced rearwardly. This rearward displacement of pressure plate 38 is transferred to firing pin 48 by contact of the pressure plate with shoulder 52 on the firing pin. The displacement of pressure plate 38 is only sufficient to energize firing pin 48 for over-travel to its cocked position and 3/32 of an inch has been proven to be suflicient.

Referring to FIG. 3, it is seen that when firing pin 48 is released from sear 68 the sear is immediately displaced rearwardly on pin 70 through the influence of spring 58 to move catch 96 rearwardly free of rear lip 94 on trigger 72. Thereby, sear 68 is free to be pivoted by spring 58 to where hook 84 slidingly contacts the outside surface of body 49 and is ready to be pressed into notch 86 when firing pin 48 reaches its cocked position. Once sear 68 is engaged to firing pin 48 it is displaced forwardly thereby relative to pin 70, as shown in FIG. 4, ready for catch 96 to engage trigger 72 When pressure on finger piece 77 is released. Thus, with firing pin 48 held cocked, lever 28 is actuatable independent thereof through the cooperation of bottom end 108 of bar with channel 110, whereby the pressure-required to pull handle 118.for unlocking barrel 18 to load another round 24 thereinto is reduced considerably to facilitate and hasten the operation. If, by chance, firing pin 48 should be released without firing a round 24 the firing pin will -be recocked When lever 28 is pulled to unlatch barrel 18 for loading another round 24 thereinto.

It is obvious that the firing mechanism of this invention can also be used very elfectively in semi-automatic firearms fed with cartridge from a magzine.

I claim:

1./In a firearm for discharge of a grenade round including a case and a projectile, a receiver, a barrel mounted on said receiver for pivotal displacement betlween a closed firing position and an open loading position and adapted to receive said round for discharge, a breechblock mounted in said receiver so as to permit set back of said case in said barrel when said round is discharged, a latch slidingly mounted in said receiver for longitudinal displacement to releasably block displacement of said barrel from the closed firing position, a firing pin slidingly disposed in said breechblock for longitudinal displacement ibetween a cocked position and a round striking position, a pin transversely disposed through said breechblock, a sear pivotally mounted on said pin to cooperate With said firing pin for releasable retention thereof in the cocked position, a trigger pivotally mounted on said pin to cooperate with said sear for actuation thereof to release said firing pin, a spring operatonally disposed between said firing pin and said sear for simultaneously biasing said firing pin to the striking position and said sear to the firing pin engaging position, and means displaceable by set back of said case for driving said firing pin to the cocked position.

2. The linvention as defined in claim 1 and including a lever slidingly mounted in said breechblock, said lever comprising a handle for manual retraction thereof and a vertically disposed bar having a top end engaged with said latch for transmitti-ng retraction of said lever thereto for unlatching said barrel and a bottom end slidingly received by a channel in said firing pin, and a rear wall of said channel contactable Iby said bottom end when said lever is retracted and said firing pin is out of the cocked position for displacement of said firing pin thereto.

3 The invention as defined in claim 1 wherein said firing pin includes a striker portion and a forwardly facing shoulder therearound, and said means includes a chamber formed between a front end of said breechblock and a front end of said receiver, a pressure plate disposed in said chamber for limited longitudinal displacement therein and for rearward displacement by set back of said case, and an orifice in said pressure plate permitting extension of said striker portion therethrough to strike said round and contact of said pressure plate with said shoulder to transmit rearward displacement of said pressure plate to said firing pin for acceleration thereof to the cocked position.

4. The invention as defined in claim 3y wherein said sear includes an elongated hole for receiving said pin to perrnit forward displacement of said sear thereon by the forward bias of said spring against said firing pin when said sear is engaged therewith, and for rearward displacement of said sear on said pin by the rearward bias of said spring against said sear when disengaged from said firi-ng pin, and a Catch extending forwardly from said sear for contact by a rearwardly extending tang on said trigger when said sear is forwardly disposed on said pin for transmitting displacement of said trigger from a normal to a pulled position to said sear for actuation thereof to release said firing pin, yand wherein said catch is disposed clear of said tang when said sear is rearwardly disposed on said pin by release of said firing pin.

5. The invention as defined in claim 4 Wherein said catch is disposed for sliding longitudinal displacement in said sear and is spring biased to a trigger engaging position, and said tang and said catch are provided With cooperating cam surfaces for engageably camrning said |a spring disposed between said sear and said trigger for biasing said trigger to the normal position and said sear toward the engaging position into sliding contact with said firing pin.

References Cited UNITED sTATEs PATENTS 2,433,309 12/ 1947 Karner 42-69 3,279,114 10/1966 Lewis et al. 42-1 (F) 3,404,478 10/ 1968 Silsby 42-1(F) BENJAMIN A. BORCHELT, Primary Examiner C. T. JORDAN, Assistant Examiner U.S. Cl. X.R. 42-1, 45 

